Device for producing a spun yarn

ABSTRACT

To manufacture a spun yarn from a loose fiber structure, devices are used in which a swirl chamber is provided between a fiber delivery channel and a yarn extraction channel. A fluid is blown into the swirl chamber. This device exhibits in the swirl chamber a guide surface, which delimits the swirl chamber downstream for the purpose of guiding fibers or fiber sectors that are swirling in the swirl chamber, the surface extending in collar fashion around the inlet aperture of the yarn extraction channel. The guide surface may form an angle of at least 30° with the axis of the yarn extraction channel in the yarn extraction direction, and outer areas of this guide surface are at a distance interval from the inlet aperture of the yarn extraction channel that corresponds to at least one tenth of the effective staple length of the fibers that are to be processed.

[0001] The invention relates to a device in accordance with the preamble of the independent patent claim. The device serves to manufacture a spun yarn from a loose fibre structure conducted to the device, whereby the fibre structure is drawn through a swirl chamber in which the fibres are subjected to a swirling flow of a fluid in order to induce rotation, and are thereby spun into a yam.

[0002] Spinning devices of the aforementioned type are known, for example, from the publications U.S. Pat. No. 5,528,895 or U.S. Pat. No. 5,647,197 (both Murata). Such devices exhibit a fibre delivery channel and a yarn extraction channel, whereby the outlet area of the fibre delivery channel is essentially aligned against the inlet area of the yarn extraction channel and the outlet aperture of the fibre delivery channel is arranged at a distance interval from the inlet aperture of the yarn extraction channel. The swirling flow is produced in the area of this distance interval. In the area of the outlet aperture of the fibre delivery channel, in addition, twist prevention means are provided (e.g. eccentric edge, over which the fibres are drawn, or in the essentially concentric pin, about which the fibres are conducted)

[0003] The inlet area of the yarn extraction channel usually has the form of a slender spindle, which rotates as appropriate, and which, like the swirling flow, can have the function of inducing rotation. An outlet channel with an essentially ring-shaped cross-section runs around the spindle. The outlet channel leads out of the cavity, equipped as a swirl chamber, and runs essentially parallel to the yarn extraction channel. The swirl chamber in this situation has essentially the same diameter as the inlet area of the outlet channel and is equipped with nozzles directed into the chamber for blowing in a fluid (e.g. air). The fluid which is blown into the swirl chamber is conducted away through the outlet channel, whereby the swirling flow produced in the swirl chamber continues around the yarn extraction channel (spindle) into the outlet channel. The swirl chamber and an inlet area of the outlet channel accordingly essentially represent a functional unit which serves to incur the rotation.

[0004] The cross-sections of the fibre delivery channel, the yarn extraction channel, and the outlet channel are small in comparison with an average fibre length. The length of the fibre delivery channel is designed in such a way that at least a part of the fibres, the forward end of which has already reached the area of the yarn extraction channel, is still being held in the inlet area of the fibre delivery channel (e.g. the between delivery rollers of a drafting device located upstream of the fibre delivery channel).

[0005] Fibres which are conducted to a device such as that described briefly heretofore are on the one hand held in the fibre structure, and so conducted from the outlet aperture of the fibre delivery channel into the yarn extraction channel essentially without rotation. On the other hand, however, in the area between the fibre delivery channel and the yarn extraction channel the fibres are subjected to the centrifugal effect of the swirling flow, as a result of which they, or at least their end sectors, are driven radially away from the inlet aperture of the yarn extraction channel. The yarns which are manufactured by the process described then also exhibit a core of fibres or fibre sectors running essentially in the longitudinal direction of the yarn without substantial rotation, and an outer area in which the fibres or fibre sectors are rotated around the core.

[0006] This yarn structure comes about, according to a model explanation, in that the forward ends of fibres, in particular of fibres of which the following sectors are still be held upstream of the fibre delivery channel, essentially pass directly into the yarn extraction channel, but that following fibre sectors, in particular if they are no longer being held in the inlet area of the fibre delivery channel, are drawn out of the fibre structure by the swirling effect and are then rotated to form the yarn. It may also arise that forward ends of fibres are splayed outwards from the fibre structure by the swirling effect, while the following end remains in the central area of the fibre structure, which leads to the loops observed in the corresponding yarns.

[0007] In any event, fibres are bound at the same time both in the yarn being formed, as a result of which they are drawn into the yarn extraction channel, as well as being subjected to the centrifugal effect, which accelerates them centrifugally, i.e. away from the inlet aperture of the yarn extraction channel, and draws them into the extraction channel. The fibre areas drawn by the swirling flow out of the fibre structure form a fibre swirl which opens into the inlet aperture of the yarn extraction channel, the longer portions of which wind in spiral fashion outwards around the spindle-shaped inlet area of the yarn extraction channel and are drawn in this spiral, against the force of the swirl in the extraction channel, against the inlet aperture of the yarn extraction channel. Fibres of which the forwards or following end is not drawn into the yarn being formed are, with a degree of probability which is greater with smaller fibres, sucked through the outlet channel and, as a result, represent undesirable fibre waste

[0008] The known spinning method described is characterised in that it allows for very high spinning speeds (up to ten times higher spinning speeds than for ring spinning methods).

[0009] On the other hand, it has proved to be difficult with this method to avoid a high fibre wastage and to obtain sufficient fibre rotation in the rotated outer area of the yarn to produce high yarn quality.

[0010] It is now the problem of the invention to propose changes related to the device with which the spinning method described heretofore can be improved. The invention therefore takes the problem of creating a device for spinning by means of a swirling flow, with which device it should be possible to achieve high yarn qualities than is possible with the known devices which serve the same purpose. In this situation, the fibre waste should be as small as possible, i.e. in any event not greater than is possible with known devices.

[0011] This problem is resolved by the device which is defined in the patent claims The invention is based on the idea of creating more rotation by increasing the swirling efficiency in the yarn, whereby the swirling efficiency is intended to be increased by the reduction of the friction between swirling fibre sectors and stationary parts of the device.

[0012] The friction reductions striven for are realised in that a substantial part of the fibre swirl is not, in the known manner, guided at the radial limits of the swirl chamber and around a spindle-shaped inlet area of the yarn extraction channel in a way which causes friction, but on a guide surface which extends around the inlet aperture of the yarn extraction channel and which forms an angle of more than 30° (for preference between 45° and 900) around the yarn extraction channel towards its axis in the yarn extraction direction. The guide surface therefore extends in collar fashion around the inlet aperture of the yarn extraction channel, whereby its outermost areas exhibit a distance interval from the inlet aperture of the yarn extraction channel which corresponds to at least a tenth of the effective staple length of the fibres which are to be processed, and for preference is greater than a sixth of the effective staple length

[0013] The effective staple length referred to heretofore is calculated in accordance with the formula published in the Japanese utility model No. 2.513.582. It is somewhat greater than an average staple length determined with an almeter.

[0014] The guide surface of the device according to the invention represents for preference a truncated cone, at the tip of which is arranged the inlet aperture of the yarn extraction channel. It has no rotation-inducing function, i.e. it does not rotate, and for this reason it is also designed for the smallest possible fibre adherence and fibre friction respectively.

[0015] The improvements in the spinning process with regard to yarn quality and fibre waste which can be achieved with the device according to the invention in comparison with devices according to the state of the art are based on the following effect: The rotating fibre ends, which according to the state of the art are arranged around the spindle-shaped yarn extraction channel and which are drawn tight around this spindle in screw fashion by the extraction of the yarn, are arranged flatter in the device according to the invention, as a result of which the tightening effect and the fibre friction associated with this are avoided. At least a part of the surfaces which radially delimit the fibre swirl, against which the fibres are pressed by the centrifugal force of the swirl flow, are further distant from the centre of the fibre swirl, and, as a result, create friction with only a smaller proportion of the swirling fibres than is the case in known devices.

[0016] The reduction of the forces with which fibres or fibre sectors are pressed against walls has the effect not only of reducing the friction but also of creating a more voluminous arrangement of the fibres in the fibre swirl. In this more voluminous fibre structure there is a greater probability than in devices of the state of the art that freely-swirling fibres (without binding in the yarn being formed) are retained in the fibre structure and are guided to the yarn instead of being driven into the outlet channel.

[0017] The friction-reducing effect of the guide surface of the device according to the invention can be increased still further if it is provided with a surface structure (e.g. orange skin) which is suitable for reducing the fibre friction still further.

[0018] Embodiment examples of the device according to the invention for the manufacture of a spun yarn from a loose fibre structure with the aid of a swirling flow are described in detail on the basis of the following figures. These show:

[0019]FIG. 1 The outlet area of the fibre delivery channel and the inlet area of the yarn extraction channel (swirl chamber area) of a device according to the state of the art for the manufacture of a spun yarn from a loose fibre structure by means of a swirling flow (section);

[0020]FIGS. 2 and 3; The likewise sectional representation of the swirl chamber area of two embodiment examples of the device according to the invention.

[0021]FIG. 1 shows the swirl chamber area according to the state of the art, with which a rotation is applied to a loose fibre structure 2 being delivered through a fibre delivery channel 1 in a swirl chamber 3, so that a spun yarn 4 is formed, which is drawn off through a yarn extraction channel 5. The swirl flow is created in the swirl chamber 3 by blowing in a fluid, e.g. air, through nozzles 6 opening tangentially into the chamber. The fluid is guided off through an outlet channel 7, whereby the outlet channel 7 exhibits a ring-shaped cross-section arranged around the yarn extraction channel 5, and its inlet area has essentially the same diameter as the swirl chamber 3, so that the swirl flow created in the swirl chamber is also continued in the outlet channel, and fibre sections 8 released from the fibre section by the centrifugal effect of the swirl flow are located in the outlet channel in spiral fashion on the outside around the stationary or rotating spindle-shaped inlet area of the yarn extraction channel 5. The swirl chamber 3 and inlet area of the outlet channel 7 represent one functional unit.

[0022] Arranged at the outlet aperture 9 of the fibre delivery channel 1 in the embodiment shown is an edge 10, serving as a rotation stopping means, which is arranged eccentrically to the yarn extraction channel 5. The principle is also known of using a pin arranged essentially concentrically to the yarn extraction channel as a rotation stopping means, said pin representing a temporary yarn core.

[0023] The diameter of the swirl chamber 3 and of the inlet area of the outlet channel 7 corresponds in the embodiment shown to about 15 to 20% of the effective staple length of the fibres which are to be processed. This means that a large part of the fibre sections moved in the fibre swirl 8 rub against the outer walls of the swirl chamber 3 and the outlet channel 5, aligned perpendicular to the centrifugal force. In the outlet channel 5 the swirling fibre sectors are brought increasingly in contact in spiral fashion with the inner wall of the outlet channel 7 (outer wall of the yarn extraction channel 5) due to the effect of the yarn intake, and are even drawn tight in screw fashion, which in turn creates friction.

[0024]FIG. 2 shows a first embodiment example of the device according to the invention. As in FIG. 1, only the area of the swirl chamber 3 is represented, i.e. the outlet area of the fibre delivery channel 1 with the outlet aperture 9 and rotation stop means 10 and the inlet area of the yarn extraction channel 5 with inlet aperture 11, as well as the swirl chamber 3 and outlet channel 7, which, as in FIG. 1, exhibits an essentially ring-shaped cross-section.

[0025] The swirl chamber 3 of the embodiment represented in FIG. 2 exhibits a guide surface 20, which delimits the swirl chamber 3 downstream and forms an angle α of at least 30° C., to advantage between 45 and 90%, with the axis of the yarn extraction channel 5. The guide surface 20 extends in collar fashion around the inlet aperture 11 of the yarn extraction channel 5 and forms for preference a truncated cone, at the tip of which is arranged the inlet aperture 11 of the yarn extraction channel 5. The radial extension of the guide surface 20 is at least as large as a tenth, and for preference larger than a sixth, of the effective staple length of the fibres which are to be processed. The outlet channel 7 connects on the outside to the guide surface 20 and exhibits at least in this area a ring-shaped cross-section, which is perceptibly larger in comparison with the state of the art. The delimitation of the swirl chamber 3 upstream runs for preference at least in part approximately parallel to the guide surface 20.

[0026] The guide surface 20 has no rotation inducing function. This means that it is stationary, as is the yarn extraction channel. The inducement of rotation is effected only by the swirl flow.

[0027] The nozzles 6, through which, in order to create the swirl flow, a fluid is pressed in a tangential direction into the swirl chamber 3, are to advantage arranged somewhat upstream of the inlet aperture 11 of the yarn extraction channel 5, and are distributed about this in a regular fashion. Their radial position is for preference relatively close to the axis of the yarn extraction channel 5, for preference closer than the radial position of the outermost guide surface areas, as is represented in FIG. 2.

[0028] As a result of the radial enlargement of the swirl chamber and the inlet area of the outlet channel in relation to the state of the art, the fibre friction at the walls perpendicular to the centrifugal force of the swirl flow is reduced. The swirling fibre sectors can also mo longer be drawn tight due to the intake of the yarn, with the result that less fibre friction occurs at the guide surface than is the case at the slim spindle of the yarn extraction channel of the known devices. Fibre friction at the guide surface can be further reduced by the fact that this is provided in an inherently known manner with a corresponding surface structure. As a result of the friction reductions brought about in this manner, the swirling fibre areas are rotated with greater efficiency than is the case in devices according to the state of the art.

[0029]FIG. 3 shows a further embodiment example of the device according to the invention, whereby the manner of representation is the same as in FIGS. 1 and 2. The same parts are also designated with the same reference numbers.

[0030] The embodiment in FIG. 3 differs from that in FIG. 2 essentially only by the angle a, which in this case amounts to 90°, so that the guide surface 20 is aligned essentially perpendicular to the yarn extraction channel 5. The swirl chamber 3 is essentially of the shape of a circular disk.

[0031] The radial extension of the guide surface 20 and the angle α of the guide surface 20 to the axis of the yarn extraction channel 5, as well as its matching to the swirl flow which is to be created, is to be determined empirically for different spinning processes, in particular for the spinning of different fibre materials. 

1. A device for the manufacture of a spun yarn (4) from a loose fibre structure (2) with the aid of a swirl flow, which has the effect of a single rotation-inducing means, whereby the device exhibits a fibre delivery channel (1) with an outlet aperture (9) and a yarn extraction channel (5) with an inlet aperture (1) located at a distance from said outlet aperture (9), as well as means for the creation of the swirl flow in a swirl chamber (3), which is arranged essentially between said outlet aperture (9) and said inlet aperture (11), which means exhibit nozzles (6) directed tangentially into the swirl chamber (3) for blowing a fluid into the swirl chamber (3) and an outlet channel (7) for conducting the fluid out of the swirl chamber (3), characterized in that the device exhibits a guide surface (20), which delimits the swirl chamber (3) downstream, for guiding fibres or fibre sectors (8) swirling in the swirl flow, said guide surface extending in collar fashion around the inlet aperture (11) of the yarn extraction channel (5), which forms an angle (α) with the axis of the yarn extraction channel (5) in the yarn extraction direction, and of which the outermost areas have a distance interval from the inlet aperture which corresponds to at least one tenth of the effective staple length of the fibres which are to be processed, and that the extraction channel (7), which exhibits a ring-shaped cross-section, connects to the outermost areas of the guide surface (20). 2 through
 6. (Cancelled) 